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# Video:Common Mathematical Symbols

Learn all about mathematical symbols and what's commonly found.See Transcript

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## Transcript:Common Mathematical Symbols

Hi my name is Bassem Saad, I'm an associate math instructor and PhD candidate at UC Davis. I'm here for About.com to go over some of the common mathematical symbols.

We'll begin with the operations. Most of these operations you've seen before, like addition, subtraction, multiplication, and division. Some other common symbols are the square root symbol, which is the inverse of the square symbol. So just as 4 times 4 equals 16, the square root of 16 equals 4. There's also the factorial symbol, denoted by the exclamation point. And the way it works is that you take the integer that you start from and you count down, multiplying every subsequent number up until you get to one. So in this example we start from 5 factorial. That will equal 5 x 4 x 3 x 2 x 1. We're done at 1 and we just multiply it all out to get 120.

### More Mathematical Symbols

There's also the percentage symbol, which is parts per hundred, which means that whatever number you have, you're going to divide it by a hundred to get the decimal form. So 30% equal .3. Finally we have the absolute value. If it's a positive number the absolute value does nothing. But if your number is a negative number, in this case negative pie, you take the absolute value and it will give you back a positive version of that number. In this case positive pie. So you just drop the negative sign.

### Mathematical Symbols for Inequalities

So we'll continue common mathematical symbols for inequalities. So we have the equal sign, less than, greater than, less than or equal to, greater than or equal to, approximately equal to, and not equal to. Some other common mathematical symbols that you may see are the plus minus symbols. They're usually handy ways of condensing multiple equations into one. For the minus plus, the order is reversed. So in this equation the plus matches up with the minus and the minus matches up with the plus. Infinity symbol is not a real number in fact but it's greater than any real number. So if x is your variable you can say that for any real number x it's always less than infinity. The therefore symbol is usually used in logical statements. So if x equals 5, therefore x is greater than 4.

For parentheses, they are usually used for either denoting the order of operations or intervals. So according to the order of operations, multiplication comes before addition or subtraction, but anything inside the parentheses comes before multiplication. Perpendicular referes to two lines that intersect with 90 degrees between them, such as this. And theta is the Greek symbol usually used to denote angles.

Those are some common mathematical symbols, thanks for watching and to learn more visit us on the web at About.com.
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